Fluid flow meter



Oct. 10, 1967 H. KARLBY ETAL 3,345,869

7 FLUID FLOW METER Original Filed Feb, 26. 1959 4 Sheets-Sheet 1 A'ITEYS Wmsrow [Z142- Oct. 10, 1967 H. KARLBY ETAL FLUID FLOW METER OriginalFiled Feb. 26. 1959 4 Sheets-Sheet 2 kw I 4 INVENTORS flaw/w [fixerMk/Q? AT T RNEYS Oct. 10, 1967 H. KARLBY ETAL 3,345,869

FLUID FLOW METER Original Filed'Feb. 26, 1959 4 Sheets-Sheet s INVENTORSfiQ-Aw/Na X2913) BY I 7M 5 A ORNEYJ Oct. 10, 196 H. KARLBY ETALY FLUIDFLOW METER 4 Sheets-Sheet 4 Original Filed Feb. 26. 1959 NOLLJIEfj m 0 1mg Jug amear INVENTORS /:/wwa finer WMsmA FZ/[i A ORNE'YS United StatesPatent 3,345,869 FLUID FLOW METER Henning Karlhy and Winston F. Z. Lee,Pittsburgh, Pa.,

assignors to Rockwell Manufacturing Company, Pittsburgh, Pa., acorporation of Pennsylvania Original application Feb. 26, 1959, Ser. No.795,755, now Patent No. 3,248,945, dated May 3, 1966. Divided and thisapplication Nov. 24, 1965, er. No. 558,151

6 Claims. (Cl. 73-231) This is a division of co-pending application Ser.No. 795,755 filed Feb. 26, 1959 for Meter, now US. Patent No. 3,248,945,and a continuation-in-part of our application Ser. No. 634,662 filedJan. 17, 1957 (now Patent No. 3,163,041), our now abandoned applicationSer. No. 717,863 filed Feb. 27, 1958, and our now abandoned applicationSer. No. 717,922 filed Feb. 27, 1958.

The present invention relates to turbine meter-s and more particularlyto improvements in such meters which render them substantially free ofmetering inaccuracies resulting from the viscosity effect of fluids ofhigh viscosity.

An example of a preferred form of turbine meter adapted for highmetering accuracy of low viscosity fluids and having no viscositycompensation is disclosed in our now abandoned application Ser. No.717,863 filed Feb. 27, 1958.

It has been established theoretically and experimentally that the meterdisclosed in said application is satisfactory tor high accuracymeasurement of fluids of low viscosity such as air, gases, water,gasoline, fuel oils, etc., but that without proper modification, it doesnot meet extremely high accuracy requirements such as 10.1% allowabledeviation over a flow range (Q /Q of for high viscosity fluids such ascrude oils of high viscosity ranges from -a minimum of 35 SUS to amaximum of 5000 SUS as required commercially, particularly where fluidsof different viscosities must be metered by the same meter. The maintrouble is due to the fact that in turbine meters of that type, thedriving forces is proportional to the square of flow (Q whereas theresisting force (F,) is proportional to an exponential power of flow'(Q) less than the square in fluids of high viscosity, the exactmagnitude of which depends upon the Reynolds number of the existing flowcondition.

As is Well known, the Reynolds number is a dimensionless expressionWhich presents the characteristics of a fluid flow in terms of thevelocity of the fluid, the dimensions ofthe element through which itflows, the density of the fluid, and the viscosity of the fluid. TheReynolds number is directly proportional to the velocity and density,and inversely proportional to the viscosity of the fluid.

In conventional practice, meter accuracy curves are plotted bygraphically presenting the ratio of the turbine velocity to the rate offlow through the meter w/ Q versus the flow rate Q. Such a curve givesinfionnation about the meter accuracy when fluid of only one viscosityis metered. If fluid of another viscosity is to be metered, anotheraccuracy curve is required to reflect the meter characteristics in fluidof the new viscosity.

After a great deal of study, it has been determined that a much moreuseful meter accuracy curve can be obtained by plotting the ratio ofturbine speed to flow rate, w/ Q versus the Reynolds number of the flowthrough the meter taken at a significant point within the meter. It hasfurther been determined that the Reynolds number of the flow through theturbine blades of the meter provides the best representation of flowcharacteristics through the meter. Thus, the blade Reynolds number isutilized as the base against which the ratio of turbine speed to flowrate w/Q is plotted to give an extremely useful accuracy curve for ameter.

3,345,869 Patented Oct. 10, 1967 To further illustrate this concept ofReynolds number accuracy curve, it will be seen that it is quitepossible for a fluid of relatively low viscosity, flowing with arelatively low velocity, to have the same characteristic of flow-andReynolds number-as a relatively viscous fluid flowing at a highervelocity. Further, each of these fluid flows will result in the sameratio of turbine speed to flow rate w/ Q so that they can be plotted asa single point in the Reynolds number accuracy curve. If, however, thetwo fluid flows were plotted as points on accuracy curves utilizing theflow rate as a base, they would he points on two separate curves, eachof which would be peculiar to only fluid of the same viscosity as thatutilized in the test.

In a conventional system of plotting the ratio of 01/ Q versus rate offlow Q, the plot must be a horizontal straight line in order for themeter to accurately meter fluid of a given viscosity at all rates offlow. If fluid of another viscosity is to be metered, another accuracycurve must be plotted and this, too, must be a horizontal straight lineif the meter is to accuractely meter fluid of that viscosity. Whenutilizing a meter accuracy curve which depicts the ratio of turbinevelocity to flow rate w/Q versus the blade Reynolds number, only asingle meter accuracy curve need be considered for fluids of allviscosities. If this accuracy curve is a horizontal straight line, themeter will accurately meter fluid of any viscosity at any flow rate.

Physically, no meter has yet been constructed which will accuratelymeter fluid over the entire range of Reynolds numbers. For all practicalpurposes, however, a range of Reynolds numbers for a specified meteringpurpose may be selected. Thus, considering the maximum and minimum flowrates and the maximum and minimum fluid viscosities desired for aparticular application, a range of Reynolds numbers may be selectedwhich will include all possible combinations of viscosity and flowvelocities within the desired limits. A meter which has a horizontalstraight line for a blade Reynolds number accuracy curve over theselected range of Reynolds num bers will, accordingly, meet thespecified metering requirements.

Experimental results indicate the turbine meter disclosed in ourcopending application Ser. No. 717,863 has a straight line bladeReynolds number accuracy curve over the high Reynolds number range.However, at the lower Reynolds numberswl1ich are a result of highviscositiesthe accuracy curve of the meter does not remain a horizontalstraight line. Instead, the Reynolds number accuracy curve of a turbinemeter of that type will have a hump in fluids of high viscosity forflows within the operating range rather than a flat curve as in fluid oflow viscosity. It is therefore necessary to introduce some specialdevice into a turbine meter of that type to eliminate the viscosityeffect of fluid of high viscosity on the meter accuracy.

The present invention therefore contemplates the provision of a specialturbine meter for accurately metering and recording the flow of viscousand extremely viscous fluids and comprises a metering turbine disposedin a conduit in the path of fluid flowing through the conduit and meansfor substantially eliminating the viscosity effect of the fluid as itpasses through the metering turbine.

With the foregoing considerations and purposes in mind, it is the majorobjectof this invention to provide means for changing the naturalReynolds number ac curacy curve of the meter disclosed in our copendingapplication Ser. No. 717,863 so that the resulting changes will flattenthe accuracy curve in the range of lower Reynolds numbers and allowfluids of higher viscosity to be accurately metered.

It is a further object of this invention to provide a novel axial flowturbine meter embodying a zero blade angle metering turbine where theprofile drag on the rotor blades acts only along the axial direction ofthe turbine, the effect of which is to eliminate the viscosity effect ofthe fluid being metered.

These and other objects of the present invention will become more fullyapparent as the description proceeds in connection with the appendedclaims and the annexed drawings wherein:

FIGURE 1 is a longitudinal sectional view of a turbine meterillustrating a further embodiment of the present invention;

FIGURE 2 is a detailed longitudinally exploded view of the embodiment ofFIGURE 1 with the meter casing broken away and the parts therein axiallyseparated for clarity;

FIGURE 3 is a diagrammatic circumferential development of the meteringturbine and guide vanes of the embodiment of FIGURE 1;

FIGURE 4 is a vectorial diagram illustrating velocities at synchronousspeed for a meter which does not compensate for fiuid viscosity;

FIGURE 5 is a plot illustrating the relation between total turbine slip(8:) due to fluid friction and the blade Reynolds number of the fluidflow; and

FIGURE 6 is a plot illustrating the blade Reynolds number accuracy curveor the relation between the angular velocity of the metering turbine perunit volume of fluid flow and the blade Reynolds number of the fluidflow.

This disclosure of the present invention will proceed with an analysisof the operation of turbine meters and the relation thereof to thepresent invention followed by a detailed description of the constructionembodying the principles of the present invention.

FIGURES 1-3 illustrate a. turbine meter constituting a practicalembodiment of the principles of the present invention for use inmetering fluids of various viscosities. Referring now to FIGURE 4,velocity vector diagrams are illustrated for the synchronous speedcondition of a turbine meter without viscosity compensation asillustrated in FIGURE 19 of the above-identified copending application(Ser. No. 717,863) and hereinafter referred to as the Type I turbinemeter.

With continued reference to FIGURE 4, the velocity v is the absolutevelocity of the fluid at the inlet to the metering element or themetering turbine, velocity v is the absolute discharge velocity of thefluid from the metering element and velocity no is the linear velocityat a radius r of the metering element rotating with an angular velocity0). Velocity v is the discharge velocity of the fluid relative to therotating metering turbine. For a particle of fluid moving along theblade with a velocity v relative to the blade, the particle wil leavethe blade at A with the velocity VR2 if the blade is at rest. If theblade is moving in direction shown with a magnitude rm, and the velocityof the particle still has a velocity v relative to the blade, andremains in contact with the blade to the end A, the absolute velocity ofthe fluid as it leaves the blade at A will be the vector sum of thevelocities v and rw. Thus, the vectorial sum of the turbine velocity andthe relative velocity will yield the absolute discharge velocity v In atheoretically perfect system where no resisting torques are encounteredin passage of the fluid through the metering element, the absolutedischarge velocity would be vectorially equal to the absolute inletvelocity of the fluid being metered since there would be no slip of theturbine. Hence, all of the fluid passing between the blades of theturbine would be metered and recorded and the value of the ratio w/Qwould be the ideal value indicated by the horizontal straight line inFIGURE 6. Under actual conditions, however, there are resisting forces,as will be described, of such nature and magnitude to cause significantturbine slip and thereby affect the accuracy of the meter unlesscompensated for. As used in this application, slip will broadlydesignate those effects which tend to bring the actual value of theratio of turbine speed to flow rate 40/ Q below the ideal value thatwould results if all the fluid passing through the turbine were meteredand recorded. This turbine slip due to prevailing forces resisting therotation of the turbine is evinced by and directly related to thetangential velocity component v of the fluid flowing through theturbine. Such a tangential velocity vectorially adds to the absoluteinlet velocity v to the resultant absolute discharge velocity v As theviscosity of the fluid changes, the resisting force is changed for agiven flow rate, resulting in a corresponding change in the tangentialvelocity 1 especially in the region of the lower Reynolds numbers. Thischange of the tangential velocity v results in turn in a varying turbineslip which is elfective to adversely affect the accuracy of meteringregistration.

The following analysis serves to exemplify the effect that the resistingforces resulting from fluid friction and mechanical friction have on theaccuracy of a turbine meter.

Analysis of the turbine meter in fluids of high viscosities By means offlow straighteners and proper design of the turbine housing andapproaching hub, the inlet velocity v to the blades of the turbine canbe assumed to be purely axial and uniformly distributed across theentire annular flow passage leading to the metering turbine.

Consider first the Type I turbine meter being steadily rotated insynchronous condition by a fluid of high viscosity and having thevelocity diagrams shown in FIG- URE 4. Since the driving force F exertedupon the turbine by the fluid can be no greater than the resisting forceF of the turbine, it will be useful to analyze the resisting forces onthe turbine and to consider their nature.

It can easily be shown by basic laws of fluid dynamics that the drivingforce F exerted on the turbine is equal to the mass rate of flow mthrough to the meter multiplied by the change in absolute tangentialvelocity v of the fluid passing through the meter or The mass rate offlow m is equal to the density of the fluid p multiplied by thevolumetric rate of flow Q or m= Q.

Now, if the turbine were in the ideal state, having no resisting forcesof any kind, the turbine would move in exact timed relation to the fluidflow and no force would be required to drive it or F would be zero. Thisis readily apparent since the fluid would not be deviated in a tangenialdirection as it passed through the turbine so that v would equal v(FIGURE 4) and vtz would equal zero.

It is unnecessary to note that this ideal condition cannot exist andthat the turbine has resisting forces which must be overcome by theforce created by the fluid flowing through the meter. In a meterturbine, as opposed to a power turbine, the forces F to be overcome bythe driving force F are relatively small. They may be convenientlyconsidered to be of two classes. The first is a resistance force F, dueto the mechanical resistance of the friction created by the bearingloads and the register load. Because of the construction of the turbinemeter with magnetic shaft suspension, magnetic register drive andlow-torque register, as fully discussed in our now abandoned application717,863, the mechanical resistance force F is held to a minimum.Further, it is relatively constant and independent of the flow rate Q.For these reasons, the mechanical resisting forces F have no appreciableeffect on the accuracy of the turbine meter in its operating flow rangeand may be disregarded for the purposes of this analysis.

The second resisting force which must be considered is the force due tothe fluid friction acting upon the rotating parts of the meter. Whilethe fluid exerts a resisting force on the spokes of the turbine, the hubof the turbine, and all other rotating parts, it has been found that thegreatest resistance force acts upon the blades of the turbine. By properdesign of the turbine, it is possible to minimize the fluid resistingforce acting upon the parts of the turbine other than the blades so thatit is only a very small fraction of the resisting force acting up theturbine blades. For the purposes of this discussion, the resisting forceacting upon all parts of the turbine except the blades may be consideredto be negligible. The resisting force Ff created by the fluid frictionacting upon the blades of the turbine should be considered in somedetail to gain an understanding of the present invention.

However, before considering the fluid friction resisting force F actingupon the turbine blades, some attention will be given to thecharacteristics of flow through the turbine meter. Considering for themoment a fluid of fixed viscosity and density flowing through the meter,at very low fluid velocities, the flow through the meter is laminar. Asthe fluid velocity increases, areas of turbulence develop until finally,the flow of fluid through the meter becomes completely turbulent.

Just when this change of flow characteristic takes place depends uponthe nature of the fluid flow passage. For any turbine meter, there isfluid velocity for any par ticular fluid below which turbulent flowcannot take place and all flow is laminar. Since this flow rate is for aparticular fluid (Le, a fixed density and viscosity) and through aparticular flow passage (i.e., the blade area of the turbine meter), itmay be expressed in terms of the Reynolds number. Thus, the Reynoldsnumber below which only laminar flow takes place is designated as thecritical Reynolds number and is so indicated on FIG- URE 3. V

The high Reynolds numbers indicate the range where the flow iscompletely turbulent. The change of the flow characteristics from alaminar flow to completely turbulent flow is not an instantaneousoccurrence at the critical Reynolds number. Rather, because of thenature of flowing fluid, there is a transition zone embracing thoseReynolds numbers immediately to the right (FIGURE of the criticalReynolds number in which the flow is partially turbulent and partiallylaminar. This area creates difliculties in predicting exactly how theturbine will behave. However, since the present invention teaches theuse of a single blade Reynolds number accuracy curve to show thecharacteristics of the meter, it is possible-by utilizing this accuracycurveto analyze the effects of the flow in the complete range ofReynolds numbers and to compensate for them in a manner to be described.

Returning now to the resisting force F acting upon the blades as aresult of the fluid friction, it is this force which creates the majordeviations from the ideal in the blade Reynolds number accuracy curve.To indicate just how these forces affect the turbine operation, thefluid resisting force F for each of the three ranges of flow patternslaminar flow, turbulent flow and transition zone-are analyzed and theirnature determined.

In the laminar flow range, the fluid friction resisting force created bythe fluid passing over the turbine blades is of a viscous nature andwill be designated F This resisting force F acts parallel to the bladesurface and so has a tangential component which is opposed to theturbine driving force F This resisting force F is the predominant causeof the change of tangenial velocity V through the turbine in the laminarflow range. To determine the nature of the resisting force F due toviscosity,

reference may be had to the basic force equation in which d'=/ Q t2'proportional to the viscosity ,u. of the fluid times the volumetric rateof flow Q, it may conveniently be expressed as where K=a proportionalityconstant. The term K hereinafter will be utilized indiscriminately todesignate any undefined proportionality constant without subscripts ormodifications except that K will be utilized when two differentconstants appear in the same equation. Two different constants in thesame equation will be designated as K and K.

Since the driving force F required to overcome the resisting force F dueto viscous friction must be equal to the resisting force F in thesynchronous condition, the last preceding equations may be equated toeach other so that PQ t2'= #Q Solving for the change in velocity due tothe viscosity effect V it will be seen that Thus, tangential velocitychange v due to the resisting force F of the viscosity effect isdirectly proportional to the fluid viscosity ,u. and inverselyproportional to the fluid density p.

In the turbulent flow range, the fluid friction resisting force whichacts upon the turbine blades is of a turbulent nature and will bedesignated F Here, too, the turbulent friction resisting force F actsalong the surface of the turbine blades so that it has a tangentialcomponent which resists the rotary motion of the turbine.

As before, the driving force F required to overcome the turbulentresisting force F is equal to the density of the fluid p times thevolumetric flow rate Q times the change in tangential velocity of thefluid through the turbine v or Further, the resisting force F, exertedon the turbine by the effect of turbulent flow is proportional to thedensity p times the square of the volumetric flow rate Q or Atsynchronous condition, the driving force is equal to the resisting forceor Solving for the change of tangential velocity v due to the turbulenteffect of the fluid Thus, the velocity change v due to the resistingforce F of the turbulent friction effect of the fluid upon the blades isdirectly proportional to the flow rate Q and is independent of theviscosity ,u of the fluid.

The resisting force F due to fluid friction in the transition zoneresults from various combinations of a turbulent friction resistingforce F, and a laminar or viscous friction resisting force F It has beendetermined that the frictional resisting force F of the fluid frictionin the transition zone may be expressed by the following equation:

The expression KpQ is of the same nature as the turbulent resistingforce F, and the expression K'nQ is of the same nature as the viscousresisting force F...-

As before, the driving force F required to overcome the fluid frictionin the transition zone may be expressed by the basic force formula Sincethe driving force F must equal the resisting force F in the synchronouscondition, the last previous equations may be equated to each other.Thus and solving for the change in tangential velocity v due to thetransition resisting force F Having determined the tangential velocitychanges in the fluid v v and v due to the fluid friction resistingforces F F and F in the laminar flow range, the turbulent range and thetransition zone respectively, it now will be determined how thesetangential velocity changes affect the meter accuracy curve. In order toconsider this situation, it must be remembered that the change intangential velocity v directly evinces turbine slip. If no resistingforces acted upon the turbine, the tangential velocity change v would bezero and the ratio of turbine velocity to flow rate w/Q would be ideal,as shown in FIGURE 6. Since it is the ratio of turbine velocity to flowrate w/ Q which must be constant in order for the turbine to accuratelymeter fluid, it is necessary to see how the changes of tangential fluidvelocity v affect this ratio. The amount that the turbine slips, orregisters below the ideal value of the ratio w/ Q, will be directlyproportional to the amount that the tangential velocity of the fluid vchanges, divided by the flow rate Q. Thus, the slip of the turbine willbe equal to Kv /Q. Since v is a linear velocity tangent to the turbine,it must be divided by some radius r to correctly express the ratio of w/Q. However, for a particular turbine, the radius r Will be a constant sothat the expression Kv Q is an accurate expression of the slip Sf interms of the change of tangential velocity v of the fluid and the flowrate Q.

Referring now to the expressions for the changes of tangentialvelocities of the fluid in the laminar range, the turbulent range andthe transition zone, it will be seen that the slip S of the turbine ineach of the ranges may be expressed merely by multiplying theexpressions for the tangential velocity changes by the term K/ Q.

Thus, in the laminar flow range, the tangential velocity change v due tothe viscosity resisting force F,,, when multiplied by the term K/ Qyields the expression for the turbine slip 8; due to the viscosity forceF, or:

wherein Thus It will further be noted that the expression of 8: makes itproportional to the fluid viscosity ,u. and inversely proportional tothe fluid density p and the flow rate Q. This expression, then, isinversely proportional to the Reynolds number R for the particularturbine meter or:

Sf R

In the turbulent range, the change in the tangential velocity 'v due tothe turbulent resisting force F when multiplied by the term-K/ Q yieldsthe expression for the turbine slip S due to the turbulent force F orUtz/ I wherein tz"= Q Thus It will be noted that in the turbulent range,the slip S is constant, which does not impair the meter accuracy.

1 In the transition zone, the tangential velocity change v due to thefluid resisting force F when multiplied by the term K/Q yields theexpression for the turbine As has been previously stated in discussingthe slip due to the viscosity resisting force F the expression Kp/ Q isinversely proportional to the Reynolds number of the particular turbinemeter involved or Referring now to FIGURE 5, it may be seen that theslip S of the meter throughout the range of Reynolds numbers is plotted.In the laminar range, the slip S varies in accordance with theexpression as the slip is due to the viscous resisting force F As theReynolds number increases to a value above the critical Reynolds number,the flow characteristics change and the slip S varies in accordance withthe expression K! S, K R

as the slip S is due to the fluid resisting force F When the Reynoldsnumber increases to a value above which the flow is completelyturbulent, an area of constant slip in accordance with the expression isentered since the slip is due to the fluid resisting force F The bladeReynolds number accuracy curve of the Type I turbine meter isrepresented in FIGURE 6. As hereinbefore described, the ideal value ofthe ratio of turbine speed to volumetric flow rate w/Q would be ahorizontal straight line over the entire range of Reynolds numbers, asindicated on FIGURE 6. However, the turbine resisting forces justdiscussed cause a slip S of the turbine which varies over the range ofReynolds numbers. This slip S when subtracted from the theoretical valueof the ratio of 01/ Q yields the Reynolds number accuracy curve. Theaccuracy curve for the Type I turbine meter, as shown in FIGURE 6, hasbeen completely verified by experimental results. It has a hump aroundthe critical Reynolds number before it reaches the flat part of thecurve. For fluids of low and medium viscosities (such as air, naturalgas, gasoline, water, thin oils, etc.) a Type I turbine meter ofreasonable size (4 inch size and above) will mainly operate on the fiatpart of the accuracy curve for a reasonable flow range. However, in caseof fluids of high viscosity, the accuracy curve will include the hump aswell as the fiat part, resulting in rather large maximum deviation. Thecritical Reynolds number of a turbine meter depends somewhat upon theinitial turbulence of the flow before entering the turbine and theparticular design of the meter. The higher the initial turbu lence, thelower the critical Reynolds number. For the turbine meter shown in saidcopending application Ser. No. 717,863, this critical value of the bladeReynolds number is found by actual test to be about 2300.

Extensive tests in a great variety of fluids (air, natural 9 gas,gasoline, Stoddard solvent, thin oil and thick oil) of the turbine meterdisclosed in said copending application Ser. No. 717,863 and severalother models designed according to the above analytical findings show agood agreement between the experimental results and theoreticalanalysis.

The embodiment shown in FIGURES 1-3 is partly identical with thestructure disclosed in said copcnding application Ser. No. 717,863. Theturbine meter illustrated therein comprises a cylindrical inlet conduitsection 20 having a faired core section 22 and an outlet conduit section26 having a faired core section 28. Core sections 22 and 28 arerespectively supported coaxially by equiangularly spaced longitudinallyextending ribs 210 and 212. Core section 28 journals a meter turbine 214and contains a drive train to a register 32. Since this structure isidentical to that disclosed in said copcnding application Ser. No.717,863 with the exception of the turbine 214, no further descriptionthereof will be given.

The turbine 214 comprises a plurality of longitudinally extending blades216 of Zero blade angle spaced equiangularly apart and individuallysupported by spokes 218 which radiate from a central hub 220. Mounted onan annular core section 230 adjacent to and upstream of turbine 214 area plurality of fixed guide vanes 232 equiangularly spaced apart relativeto the axis of turbine 214 and curved to impart a selected direction ofinlet fluid velocity to the turbine rotor with least disturbance (FIGURE3). The annular core section 230 is coaxial with the turbine 214 and ismounted between the inner end of the faired core section 22 and collar234 by machine screws 236. Thus, fluid to be metered passes into theannular channel 238 and is directed into the turbine 214 by the fixedvanes 232.

Referring now to FIGURE 3, the blade angle of the individual turbineblades 216 of the metering turbine 214, as measured from the axialdirection, is shown to be reduced to zero as hereinbefore described. Bythe addition of the stationary flow directing guide vanes 232 upstreamof the metering turbine, a tangential component to the inlet velocity ofthe fluid entering the metering turbine is obtained. As hereinbeforediscussed in the analysis of the Type I turbine meter, the resistingforces due to the fluid friction F on the turbine blades act along thesurface of the blades. Due to considerations of fluid dynamics, theblades of the Type I meter are provided with a blade angle [3 measuredfrom the axial direction which is in the range of 20 to 60. By this TypeI meter blade construction, it will be appreciated that since the fluidfrictional resisting force F act along the surfaces of the blades, thenthey have a substantial component (F sin 8) which acts in a tangentialdirection to oppose the rotation of the turbine and cause turbine slip.

In the metering turbine with a zero blade angle as described in theembodiment of FIGURES 1-3 of the present invention, the tangentialcomponent of the fluid friction resisting force F is consequently zero(F sin =0*) and the entire force Ff due to fluid friction is taken up bythe low-friction thrust bearings of the turbine. Since the thrust on thelow-friction thrust bearings due to the fluid force F produces only verysmall resistance to the rotation of the turbine because of the extremelylow coeflicient of bearing friction on the small moment arms at thebearings, it produces no appreciable metering inaccuracies. Thus, thezero blade angle turbine is subject to much less viscosity effect thanthe turbines with substantial blade angles.

In order to drive the zero blade angle turbine 214, stationary flowdirecting vanes 232 function to establish a tangential velocitycomponent to the fluid entering the turbine so that the turbine will bedriven at speeds acceptable for accurate metering.

With continued reference to FIGURE 3 which shows the blade profiles ofthe stationary vanes 232 and the zero blade angle turbine 214, the fluidenters the stationary 7 vanes or stator 232 with a velocity V which ispurely axial and uniformly distributed. The stationary vanes 232efficiently redirect the fluid so that it emerges with an exit velocityV which has a tangential velocity component. This redirected velocity Vbecomes the turbine inlet velocity V and provides the driving forcewhich drives the metering turbine 214 with an angular velocity to andthe blades 216 with a linear velocity rw. By this construction, theturbine exit flui-d velocity V relative to the blades 216 of the turbineis axial. Thus, the fluid resisting force F acting along the surface ofthe blade exerts no restraining force opposite to the direction ofrotation of the turbine, but rather, causes only an increased thrust onthe turbine bearings.

The embodiment of FIGURES 1-3 provides for the employment of alongitudinal extending zero blade angle turbine. By this structure, thetangential component of the profile drag is zero and thus no elfectiveresistance to the turbine rotation by the effect of fluid friction isexerted on the blades of the turbine.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. An axia-l flow impulse turbine meter comprising a housing, a bladedturbine metering rotor rotatably mounted in said housing for driving aregistering mechanism, means for guiding motive fluid through saidhousing in a solid annular, axially flowing stream extending parallel tothe axis of rotation of said rotor, said rotor having a plurality ofzero blade angle radial blades extending in the path of said annularstream and being contained in planes which extend radially from therotor rotational axis, and a circumferential row of equiangularly spacedapart fixed blades mounted in said housing in the path of said streamand at a predetermined distance upstream from said rotor blades, saidfixed blades having outlet portions extending at an acute angle withrespect to the rotor rotational axis to provide the axially flowingstream entering said rotor with a tangential velocity component fordriving said rotor, said stream leaving said fixed blades and enteringsaid rotor being oriented relative to said zero angle blades to effectthe translation of substantially the entire magnitude of the fluidfrictional force acting on said rotor into an axial thrust.

2. The axial flow turbine meter defined in claim 1 wherein said rotor isrotated substantially only by said tangential velocity component andwherein the inner and outer boundaries of said annular stream areuniformly diametered at least from a region that is upstream from saidfixed blades to the region where it enters said rotor.

3. The axial flow turbine meter defined in claim 2 wherein said fixedblades are arranged about an axis that axially aligns with therotational axis of said rotor said fixed blades being curved to providesaid outlet portions and having straight inlet portions extendingsubstantially parallel to the rotor rotational axis.

4. The axial flow turbine meter defined in claim 3 comprising fixed vanemeans disposed a predetermined distance upstream from said fixed bladesand being disposed in said annular stream to direct fluid entering saidfixed blades with a velocity that is essentially axial with respect tothe axis about which said fixed blades are disposed.

5. The axial flow turbine meter defined in claim 4 wherein said motivefluid guiding means comprises a core structure disposed in said housingin axial alignment with the rotor rotational axis and defining the innerboundary of said annular stream, wherein said vane means comprises aplurality of angularly spaced apart guide vanes mounted on said corestructure and extending radially in said annular stream, and whereinsaid fixed blades are mounted on said core structure.

6. An axial flow impulse turbine meter comprising a housing having apair of axially aligned, centrally separable sections, a bladed turbinemetering rotor rotatably mounted in said housing for driving aregistering mechanism, means comprising a core structure disposed insaid housing in axial alignment with the rotor rotational axis forguiding rotor fluid through said housing in a solid annular, axiallyflowing stream extending parallel to the axis of rotation of said rotor,said core structure defining the inner boundary of said annular streamand having axially aligned, axially separable, abutting sections, saidrotor having a plurality of zero blade angle radial blades extending inthe path of said annular stream and being contained in planes whichextend radially from the rotor rotational axis, a circumferential row ofequiangularly spaced apart fixed blades mounted on one of the corestructure sections within said housing and being arranged about an axisthat axially aligns with the rotational axis of said rotor, said fixedblades being disposed in the path of said stream and at a predetermineddistance upstream from said rotor blades to provide the axially flowingstream entering said rotor with a tangential velocity component fordriving said rotor, said rotor being rotated substantially only by saidtangential velocity component, the inner and outer boundaries of saidannular stream being uniformly diametered at least from a region that isupstream from said fixed blades to a region where it enters said rotor,and fixed vane means comprising a plurality of angularly spaced apart,radially extending guide vanes mounted on the other of said corestructure sections at a predetermined distance upstream from said fixedblades and being disposed in said annular stream to direct fluidentering said fixed blades with a velocity that is essentially axialwith respect to the axis about which said fixed blades are disposed,said core structure being provided with an annular periphery ofessentially constant diameter axially between the upstream edges of saidfluid guide vanes and the downstream edges of said fixed blades, saidrotor being coaxially mounted only in one of said housing sections, andsaid core structure being coaxially mounted only in the other of saidhousing sections.

References Cited UNITED STATES PATENTS 1,152,952 9/1915 Kepka 73231 X2,146,827 2/1939 Kruspi 73-231 X 2,934,947 5/1960 Buck 73231 X 3,043,1397/1962 Waugh et al 73--194 3,063,295 11/1962 Dowdell 73-194 3,144,7688/1964 Gehre 73229 X JAMES J. GILL, Acting Primary Examiner.

RICHARD C. QUEISSER, Examiner.

E. D. GILHOOLY, Assistant Examiner.

1. AN AXIAL FLOW IMPULSE TURBINE METER COMPRISING A HOUSING, A BLADEDTURBINE METERING ROTOR ROTATABLY MOUNTED IN SAID HOUSING FOR DRIVING AREGISTERING MECHANISM, MEANS FOR GUIDING MOTIVE FLUID THROUGH SAIDHOUSING IN A SOLID ANNULAR, AXIALLY FLOWING STREAM EXTENDING PARALLEL TOTHE AXIS OF ROTATION OF SAID ROTOR, SAID ROTOR HAVING A PLURALITY OFZERO BLADE ANGLE RADIAL BLADES EXTENDING IN THE PATH OF SAID ANNULARSTREAM AND BEING CONTAINED IN PLANES WHICH EXTEND RADIALLY FROM THEROTOR ROTATIONAL AXIS, AND A CIRCUMFERENTIAL ROW OF EQUIANGULARLY SPACEDAPART FIXED BLADES MOUNTED IN SAID HOUSING IN THE PATH OF SAID STREAMAND AT A PREDETERMINED DISTANCE UPSTREAM FROM SAID ROTOR BLADES, SAIDFIXED BLADES HAVING OUTLET PORTIONS EXTENDING AT AN ACUTE ANGLE WITHRESPECT TO THE ROTOR ROTATIONAL AXIS TO PROVIDE THE AXIALLY FLOWINGSTREAM ENTERING SAID ROTOR WITH A TANGENTIAL VELOCITY COMPONENT FORDRIVING SAID ROTOR, SAID STREAM LEAVING SAID FIXED BLADES AND ENTERINGSAID ROTOR BEING ORIENTED RELATIVE TO SAID ZERO ANGLE BLADES TO EFFECTTHE TRANSLATION OF SUBSTANTIALLY THE